1. Field of the Invention
The present invention relates to a method of deriving a scattered wave using T-matrix method.
2. Description of the Related Art
In various optical fields, a method of deriving a scattered wave from a scatterer having a size smaller than a wavelength is known. For example, according to a derivation method by Mie scattering, the scattered wave generated by a spherical particle can be derived at high speed and with high accuracy. In a method of deriving an electromagnetic field that is represented by FDTD method (Finite-difference time-domain method) or a boundary element method, whole or a part of a derivation region is divided in a mesh manner, and a dielectric constant is defined for all of the grating points to perform a propagation calculation of light.
T. Wriedt et al., “Light scattering by single erythrocyte: Comparison of different methods” discloses DDA (discrete-dipole approximation) method, which treats a scatterer as a cluster of dipoles to be divided to be able to handle the scatterer having an arbitrary shape. T. Wriedt et al., “Light scattering by single erythrocyte: Comparison of different methods”, and T. Wriedt, “Using the T-Matrix Method for Light Scattering Computations by Non-axisymmetric Particles: Superellipsoids and Realistically Shaped Particles” discloses T-matrix method that is capable of strictly handing a multiple scattering generated by spherical particles, and it also discloses the T-matrix method that is applicable to an aspherical particle.
However, in the derivation method of the scattered wave using a conventional derivation method of an electromagnetic wave, it can be derived only on a limited condition. For example, in a method using the Mie scattering, a perfect sphere is only handled, and a multiple scattering when a plurality of particles exist cannot be handled. In addition, due to a derivation cost, a model may be significantly limited depending on a method in accordance with a computer environment. For example, in the derivation method of the electromagnetic wave that is represented by the FDTD method or the boundary element method, since whole or a part of the derivation region needs to be divided in the mesh manner, a derivation time or a consumption amount of a memory in a computer is enormous. In the DDA, since a fine dipole needs to be closely arranged inside the scatterer, the derivation cost is enormous. Thus, the number of the settable scatterers is limited, and there may be a case where the mesh division enough to express the fine structure of the scatterer or the arrangement of the dipole is impossible. Recently, as disclosed in T. Wriedt et al., “Light scattering by single erythrocyte: Comparison of different methods”, and T. Wriedt, “Using the T-Matrix Method for Light Scattering Computations by Non-axisymmetric Particles: Superellipsoids and Realistically Shaped Particles”, there is a derivation method that can also be applied to an aspherical particle by the improvement of the T-matrix method, but it can only handle a particle having a shape similar to a spherical shape such as an ellipsoid.